1. Field of the Invention
The present invention relates to an electrical connector such a waterproof one used for a motor vehicle, more particularly to a low coupling-force connector. The connector is reduced in size and cost with a sufficient reliability.
2. Related Art
A waterproof connector used for a motor vehicle generally requires a larger mating force than a non-waterproof one. Because, the waterproof connector must have a watertight structure with a packing made of rubber or the like. Recently, such connectors have a lot of terminals, which requires a further larger mating force. This disadvantageously causes incomplete mating of connecters, incorrect electrical connection, or insufficient watertightness.
To improve the situation, a pair of connectors called as a bayonet or spigot type are provided. The pair of connectors are provisionally engaged with each other, and then a turnable member provided on one of the connectors is turned to move the connectors toward each other for completion of the engagement. This requires a comparatively smaller engagement force since the connectors turns when mated in waterproof connectors having multi-terminals that otherwise would need a larger engagement force.
FIG. 9 shows a pair of male and female connectors 40, 41 disclosed in Japanese Patent Application Laid-open No. H-4-132178. The connectors 40, 41 accommodate terminals 42 or 43. The male connector 40 has a turnable locking hood 44 (turnable member) having an inner wall formed with a protrusion 45. The female connector 41 has an outer surface formed with a helical groove 46. The protrusion 45 enters an open end of the helical groove 46.
The locking hood 44 turns from an initial provisional engagement state of the connectors 40, 41, so that the protrusion 45 engages the helical groove 46 to provide a cam action to move the female connector 41 until the protrusion 45 reaches an end of the helical groove 46 to complete engagement of the connectors 40, 41 for electrical connection thereof.
The turning force of the locking hood 44 provides a larger mating force by the helical groove 46, advantageously enabling an easy mating operation of the connectors 40, 41.
In this case, an operator generally knows the engagement completion of the connectors by recognition of a change in turning torque of the turnable member. However, there is a possibility of incomplete engagement of the connectors, because the recognition of the engagement depends on feeling of the operator.
This is, the operator may possibly stop the turning of the turnable member before the projection reaches the end of the helical groove, causing incomplete engagement of the connectors not to keep waterproofness of the connectors against external water.
Furthermore, when the connectors are mounted in a motor vehicle, even after the complete engagement of the connectors, an external force or vibration may possibly cause loosening of the turning member to make the engagement incomplete, bringing about incorrect electrical connection or disengagement of the connectors.
To solve the problem, an electrical connector proposed in U.S. Pat. No. 5,980,293, as shown in FIG. 10, has a pair of male and female connectors 50. The male connector has a turnable member 51 that engages with the female connector. After initial provisional mating of the male and female connectors 50, the turnable member 51 turns to move the male connector to completely engage the connectors with each other for electrical connection thereof. Furthermore, an additional engagement recognition piece 52 is provided to confirm the complete engagement of the male and female connectors. When the turning of the turnable member 51 completely engages the male and female connectors with each other, a protrusion 54 defined in the engagement recognition piece 52 is locked in a concave 55 formed in the turnable member 51. Meanwhile, when the turning of the turnable member 51 incompletely engages the male and female connectors with each other, the protrusion 54 is not locked in the concave 55. Thus, an operator recognizes whether the connectors have engaged completely with each other by the engagement state of the protrusion 54 of the engagement recognition piece 52 with the concave 55 of the turnable member 51.
Japanese Patent Application Laid-open No. 2001-6814 proposes a pair of connectors that are pushed axially against each other when mated. The connectors have an engagement ring that is turned when the connectors are disengaged. Moreover, a locking mechanism is provided for the connectors.
As shown in FIG. 11, the connectors have a cylindrical plug 60, a counter plug 61, and a bayonet ring 62. The counter plug 61 has a housing 63 around which the bayonet ring 62 is turnably attached. The bayonet ring 62 locks the plug 60 to the counter plug 61. The plug 60 is pushed against the housing 63 of the counter plug 61 until a locking mechanism provided in the bayonet ring 62 locks to the housing 64 of the plug 60. The plug 60 has a strap 65 for locking the turning of the bayonet ring 62 at the complete engagement state of the connectors. When the connectors 60, 61 are disengaged from each other, the bayonet ring 62 is turned around the housing 63 of the counter plug 61 to release the locking.
However, these conventional arts require additional parts or operational works to confirm complete engagement of a pair of connectors, increasing a production cost and decreasing an operational efficiency thereof.